| AAEMs |
K (K2CO3 and KOH) |
increased reaction
rate |
Advantages: |
hydrogen
and syngas |
(166, 243−246) |
| high mobility |
| inherently found in biomass |
creating micropore
structure on carbon feed |
reducing tar and soot ingredients |
| increased reaction rate |
|
| Disadvantages: |
|
| volatility of potassium species (i.e., KCl) |
|
| deactivation of potassium |
|
| agglomeration at higher temperatures above 800 °C |
|
| difficulty
in catalyst recovery |
|
| transition metal catalysts |
Ni |
high activity |
Advantages: |
reducing tar content |
(195, 247, 248) |
| low cost compared to other transition metal
precursors |
| Disadvantages: |
enhancing
the quality of gaseous product |
| deactivation
caused by sintering and carbon formation |
|
| scarce sources such as Pt, Ru, Rh, Ir, and Pd |
|
| carbon-based catalysts |
biochar, activated char |
large specific surface area (SSA) |
Advantages: |
tar conversion |
(210, 212, 213, 222, 249) |
| high reliability |
| porous structure |
low cost |
| simple recovery upon deactivation |
| functional groups |
good catalytic activity |
| good catalytic activity |
Disadvantages: |
| requires modification for use as the support |
| declining active sites over time |
| natural mineral catalysts |
dolomite |
relatively favorable catalytic
activity |
Advantages: |
increasing
the quality of gaseous product |
(128, 194, 243, 250) |
| low
cost |
| abundance |
providing 95% and more tar reduction |
| Disadvantages: |
| require further cleaning process for accessing the
active component
of the material |
| decrease in the mechanical
strength with time |
| catalyst
alternatives to waste byproducts |
material
that has CaCO3 content such
as egg shell, oyster shells, etc. |
abundance |
Advantages: |
increasing H2 yield |
(228, 229, 251) |
| high CaCO3 content |
low cost |
| minimizing waste product |
promising
CO2 absorption |
| Disadvantages: |
|
| deactivation due to particle agglomeration |
|
| require modification of the active
site |
|
